Folding boxes and blanks, particularly in regard to sealing by means of a thermoplastic coating preapplied to both sides thereof



Nov. 15, 1966 T. R. BAKER 3,

FOLDING BOXES AND BLANKS, PARTICULARLY IN REGARD TO SEALING BY MEANS OFA THERMOPLASTIC COATING PREAPPLIED TO BOTH SIDES THEREOF I Filed Feb.25, 1965 2 Sheets-Sheet 1 COATED ON 80TH J/DE-S' WITH A THERMOPLASTICFILM INVENTOR. 7/70/7706 R. Baker ATTORNEY Nov. 15, 1966 BAKER 3,285,494

FOLDING BOXES AND BLANKS, PARTICULARLY IN REGARD TO SEALING BY MEANS OFA THERMOPLASTIC COATING PREAPPLIED TO BOTH SIDES THEREOF 2 Sheets-Sheet2 Filed Feb. 25, 1.965

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INVENTOR. T/wmas R. Baker United States Patent 3,285,494 FOLDING BOXESAND BLANKS, PARTICULARLY IN REGARD TO SEALING BY MEANS OF ATHERMOPLASTIC COATING PREAPPLIED T0 BOTH SIDES THEREOF Thomas R. Baker,Los Altos, Calif., assignor to Kliklok Corporation, New York, N.Y., acorporation of Delaware Filed Feb. 25, 1965, Ser. No. 435,212 5 Claims.(11. 229-36) Folding boxes for the packaging of frozen foods or othermoisture or liquid containing contents are customarily coated with afilm of a thermoplastic material. This material may be a wax compositionhaving a relatively high melting point, as are presently available fromnearly all major oil refining companies, or it may be a synthetic resin,for example polyethylene.

These coatings or films are extremely thin, the thickness being of theorder of two to four hundredths of a millimeter per film. Arepresentative box sample of 0.34 mm. thickness measured 0.41 mm. with acoating on both surfaces. It is common practice to make the insidecoating, whose principal purpose is to liquid-proof the board, somewhatthicker than the outside coating which is generally treated to impart ahigh gloss thereto, which enhances the appearance of printing orlithographic art work on the box.

It is the practice in the United States box industry to express thecoating or film thickness .in terms of weight per surface area. Forexample, the aforementioned box which had a board caliper of 14 points(14 thousandths of an inch) uncoated, had a total of seven pounds ofhigh melting points applied to 1000 sq. feet of board (3.5 kg./ 100 sq.meters), more particularly at the rate of four pounds per one thousandsquare fee-t for the inside and three pounds per thosuand square feetfor the outside. With both coatings the caliper increased to 17 points.In metric terms the four pound coating amounts to approximately 2 kg.per 100 square meters and the three pound coating to 1.5 kg. per 100square meters.

Boxes of the aforementioned kind were previously sealed either bymechanical means, such as flaps or tabs inserted into slits or behindedges, followed generally by overwrapping, or they were sealed by meansof an adhesive applied prior to, or at the time of, scaling inpredetermined areas.

The thickness of the applied adhesive layer exceeds the thickness of theaforementioned coating considerably and because of its thickness theadhesive is capable of bridging gaps in the closure.

For example, it was possible by conventional sealing procedure toproduce a reliable bond between a flat panel, for example a cover flapand the box end wall over which the flap was folded, even though theplane of the box end wall was uneven, as a result, for example, ofcorner flaps overlying certain portions of the end wall. The differencesin thickness correspond to approximately the blank caliper, or slightlymore in the event additional unevenness is produced by the insertion ofcorner flap portions through slits in the box end wall.

The present invention is based on the recognition that a reliable sealcan be produced without any additional adhesive by means of the thinboard coating alone even though the coating possesses no gap bridgingproperties whatever, which is readily appreciated when one compares thethickness of the total available coating material (for example 0.07 mm.)with the caliper of the board in uncoated condition (for example 0.34mm.).

Perhaps the most extensively used form of frozen food box is the one inwhich the end Wall structure comprises a box body end wall panel overwhich two corner lock flaps are folded which partially extend throughslits in the 3,285,494 Patented Nov. 15, 1966 ICC end panel to form amechanical corner lock. The resulting unevenness of the box body endwall exceeds the thickness of the board.

According to the present invention the unevenness is reduced to zero andall major portions of the end Wall are brought into the same plane bymechanical bowing out of the end wall panel, the bowing out, in turn,being produced automatically by a particular configuration of the foldline along which the end wall panel is articulated to the bottom panel.

More particularly, the fold line comprises three portions, viz., acentral portion and two terminal portions. The terminal portions are outof line with the central portion so that an imaginary chord passingthrough the far ends of the terminal portions is spaced from, andsubstantially parallel to, the central portion, the offset of thecentral portion with respect to the chord being to the outside of thebox.

I am of course aware of the fact that it is conventional practice in theart of folding box making to offset fold lines of certain panels withrespect to fold lines of other panels. It is also known to bow foldlines in order to arch a box wall so as to sustain considerable sealingpressure without the danger of caving in.

In none of the known instances however was the present inventions goalattained, namely the sealing of box panels by means of its thin water ormoisture proofing coating. It therefore appears that the bowing ofportions of an otherwise uneven box wall for the purpose of reducing theunevenness in combination with the thin thermoplastic coating produces aheretofore unattainedeffect and eliminates the need for the applicationof special adhesives. This, in turn, simplifies the closing andmachinery greatly. j

The objects, features and advantages of this invention will appear morefully from the detailed description which follows accompanied :bydrawings showing, for the purpose of illustration, a preferredembodiment of the invention. The invention also resides in certain newand original features of construction and combination of elementshereinafter set forth and claimed.

Although the characteristic features of this invention which arebelieved to be novel will be particularly pointed out in the claimsappended hereto, the invention itself, its objects and advantages, andthe manner in which it may be carried out, maybe better understood byreferring to the following description taken in connection with theaccompanying drawings forming a part of it in which:

FIG. 1 is a plan view of a folding box blank incorporating theinvention, only one-half of the blank being shown;

' FIG. 2 is an elevational end view, partly in section, of the closedbox;

FIG. 3 is a section taken on line 3-3 of FIG. 2; and

FIG. 4 is a perspective view, partly in section, of the sealed box.

In the descriptio and in the claims various details will be identifiedby specific names for convenience. The names, however, are intended tobe generic in their application. Corresponding reference charactersrefer to corresponding figures of the drawings.

The drawings accompanying, and forming part of, this specificationdisclose certain specific details of con structio for the purpose ofexplanation of broader aspects of the invention, but it should beunderstood that structural details may be modified in vanious respectswithout departure fi'om the principles of the invention and that theinvention may be incorporated in other stnuctunal forms than shown.

The blank B shown in FIG. 1 comprises a central series of panels, moreparticularly a front wall panel 11, a bottom panel 12, a rear wall panel13, a cover panel 14 and a cover front flap 15 articulated to oneanother along a front bottom fold line 16, a rear bottom fold line 17, acover hinge line -18, and a front fiat fold line 19, respectively.

Two lateral series of panels extend from certain of the aforesaidpanels. Only one-half of the symmetrical blank is shown in FIG. 1, itbeing understood that the half which is not shown is a mirror image ofthe illustrated The lateral series of panels comprises, in order, acorner lock tflap 20, a box body end panel 21, a turther corner flapshaped as a lock flap -22, and a cover flap 23 articlulated to thecentral panels along a corner fold line 24, a bottom end told line 25, acorner fold line 26, and a cover end flap fold line 27, respectively.

The corner lock flaps 20 and 22 are shown to have the familiar lockconfiguration as indicated at 28, and the end panel 21 comprisesinternal cuts or slits 29 into which the male lock elements 28 areinsertable.

The paperboard from which the blank B is cut is coated on both surfaceswith the usual thin coats of thermoplastic material which may be ahighmelting point wax or a synthetic resin such as polyethylene. Thethickness of the coating or film is of the order above given.

The blank B is converted into box form B in the usual manner by foldingthe wall panels 11, 13 and 21 upright with respect to the bottom panel,folding the lock flaps 20 and 22 over the outside of the end panels 21,inserting the lock tips into the slits 29 and forcing the very points ofthe tips behind the flat portions 30 of the slits 29. This is knownprocedure.

The box B is then filled and the cover [folded into closing positionready [for sealing. In the closing position the cover panel 14 liesparallel to the box bottom and the cover flaps 15 and 23 overlie thetrout and ends of the box (FIGS. 2 and 4).

In order now to produce a good adhesive bond between the cover flap 23and the end panel structure 20, 21, 22 in spite of the absence of gapbridging properties of the thermoplastic films, the central portion ofthe end wall 21 is bowed out between the lock flaps 20 and 22, as bestshown in FIG. 3. This is accomplished by a particular configuration oroutline of the bottom end fold line 25. v

The bottom end fold line comprises a central straight portion 31 betweenterminal portions 32, '33. The terminal portions 32, 33 extend at anangle a with respect to the central portion and terminate at the cornerpoints 34, 35. An imaginary chord 36 may be drawn connecting these twopoints. The chord is indicated by a dashdouble-dot line. This chord line36 is not physically present in the blank, but is shown in the drawingsto indicate the outward ofiset d of the bottom told line portion 31 withrespect to the location occupied by the bottom end fold line inconventional boxes.

The length 1 of the terminal portions 32, 33 is somewhat longer than, orequal to, the length 1 of the bottom edge 37, 38 of the lock flaps 20,22.

The effect of this arrangement is illustrated in FIG. 3. It is seen thatupon folding of the end panel 21 the central portion of the end panel 21bows out along a length L. The cover flap 23 can therefore make tullcontact with the panel 21, particularly in the critical area immediatelyabove the bottom told line 25, except for small spaces or depressendareas 39, 40 immediately adjacent the lateral edges of the lock flaps.

- Tests were conducted to compare the performance of boxes embodying theinventio with conventional boxes having straight bottom end fold linesand, accordingly, an end wall structure in which the end wall and thecorner flaps lie in difierent planes.

' The tests proved that in the boxes embodying the invention a fibertearing bond was obtained between the cover flap and the box end closeto the bottom fold line and substantially uniformly across the entirewidth of the box end.

In conventional boxes having a straight bottom end fold line the lengthof the fiber tearing area was considerably shorter.

It was further noticed that in the boxes embodying the invention asecure fiber tearing bond was consistently formed between the cover flapand the corner flaps immediately above the level of the box bottom. Byway of contrast, in none of the conventional boxes was a bond formed atthat area. A reasonable explanation for this appears to be thatexert-ion of sealing pressure on the corner flap tends to bow the flapstowards the inside of the box into contact with the end panel which liesin a plane farther removed than the corner flaps. The edges of thecorner flaps then act as a fulcrum causing the terminal portions of thecover flap to flare up and thus move out of contact with the face of thecorner flaps.

In distinction, no such bowing of the cover flap occurs in the boxesembodying the invention. The cover flap remains fiat and adheres notonly to the end wall, but also to the corner flaps.

What is claimed is:

1. The end construction of a folding box of paperboard oompmising abottom panel; a pair of side panels articulated to opposite sides of thebottom panel, on end panel articulated to one end of the bottom panelalong a bottom end fold line and :a pair of corner lock flapsarticulated to said side panels along corner fold lines and folded overthe end panel; a cover panel; anda cover flap articulated to said coverpanel in a position to overlie said end panel and said corner flaps atleast partially, in which said bottom end fold line comprises threeportions, viz., a central portion and two terminal portions, saidcentral portion being ofiset toward the outside of the box with respectto a imaginary chord connecting the far ends of the terminal portions, acurvature resulting in the end panel when folded at said bottom end foldline with respect to the bottom panel, said curvature being convex asviewed from the box outside which curvature brings the central portionof the wall panel into substantially the same plane as the corner lockflaps which overlie the end portions of the wall panel adjacent saidcorner fold lines.

2. A folding box of paperboard coated on both sides with a film of athermoplastic material, the box comprising a bottom panel; a front paneland a rear panel articulated to the sides of the bottom panel along afront and a rear bottom foldline, respectively; a pair of end panelsarticulated to the ends of the bottom panel along bottom end fold lines;corner lock flaps articulated to said front and rear panels along cornerfold lines, folded to overlie the said end panels except for a flapportion which extends through slits in the respective end panels; acover panel articulated to said rear panel along a cover hinge line; anda pair of cover side flaps articulated to the ends of the cover panel,said cover side flaps overlying the outside surface of the said endpanels and that portion of the corner flaps which overlies the endpanels and being bonded thereto by the thermoplastic coating material onthe inside of the cover side flaps and on the outside of the end panelsand corner lock flaps, the said bottom end told lines comprising, each,a central line portion and terminal line portions, the distance betweenthe central portions of opposite lines being greater than the distancebetween imaginary chords connecting the far ends of the respectiveterminal line portions, causing the central end panel portion lyingabove the central bottom end line portions to bulge out substantiallyinto the plane of the said overlying corner lock flap portions.

3. In a folding box blank of paperboard coated on both sides with afilmof thermoplastic material, the blank comprising a bottom panel; afront panel and a rear panel articulated to opposite sides of the bottompanel along a front and a rear bot-tom fold dine, respectively, andhaving slots therein for insertion of portions of the corner lock flapshereinafter recited; a pair of end panels articulated to opposite endsof the bottom panel along bottom end fold lines; corner lock flapsarticulated to the ends of said front and rear panels along corner foldlines; a cover panel anticulated to said rear panel along a cover hingeline; and a pair of cover side flaps articluated to opposite ends of thecover panel along side flap fold lines, the improvement which ischaracterized by the said bottom end fold lines, each, comprising acentral line portion and a terminal line portion at each end of thecentral line portion, the distance between the central portions ofopposite nSold lines being greater than the distance betweenhypothetical chords connecting the far ends Olf the terminal l-ineportions, the end panels when folded along said bottom end fold linesbeing bowed out centrally.

4. A folding box blank as defined in claim 3 in which the "length ofeach terminal bottom end fold line portion exceeds the length of thebottom edge of the respective corner iock flap as measured in line witha hypothetical extension of the respective front and rear bottom foldline.

5. A folding box of paperboard comprising a box body, a box cover panelarticulated to said body, and a cover flap articulated to said cover ina position to overlie a body Wall, said body wall being constructed of awall panel and two corner lock flaps over-lying said wall panel, saidwall panel being articulated to the remainder of the box body along abottom fold line comprising three portions, viz., two terminal portionsand a central portion, an imaginary chord connecting the far ends of theterminal portions being offset towards the box inside in relation to thecentral portion causing the central panel portion above said centralfold line portion to bulge out when the panel is folded along saidbottom fold line, the length of the terminal portions being such as tolimit the bulge of the wall panel to that portion which lies between theoverlying corner flaps.

References Cited by the Examiner UNITED STATES PATENTS 1,554,099 9/1925Ko'l be 229- 2,265,326 12/1941 Stopper 22933 X 2,809,776 10/1957Barrington et a1. 229-35 X 2,833,;4 59 5/1958 Greene 2-2935 3,165,2531/1965 Adams et a1. 22936 X 3,176,899 4/1965 McMahon 22936 X 3,206,0989/ 1965 Stenger et :al. 22936 JOSEPH R. LECLAIR, Primary Examiner.

D. T. MOORH EAD, Assistant Examiner.

1. THE END CONSTRUCTION OF A FOLDING BOX OF PAPERBOARD COMPRISING ABOTTOM PANEL; A PAIR OF SIDE PANELS ARTICULATED TO OPPOSITE SIDES OF THEBOTTOM PANEL, AN END PANEL ARTICULATED TO ONE END OF THE BOTTOM PANELALONG A BOTTOM END FOLD LINE AND A PAIR OF CORNER LOCK FLAPS ARTICULATEDTO SAID SIDE PANELS ALONG CORNER FOLD LINES AND FOLDED OVER THE ENDPANEL; A COVER PANEL; AND A COVER FLAP ARTICULATED TO SAID COVER PANELIN A POSITION TO OVERLIE SAID END PANEL AND SAID CONRNER FLAPS AT LEASTPARTIALLY, IN WHICH SAID BOTTOM END FOLD LINE COMPRISES THREE PORTIONS,VIZ., A CENTRAL PORTION AND TWO TERMINAL PORTIONS, SAID CENTRAL PORTIONBEING OFFSET TOWARD THE OUTSIDE OF THE BOX WITH RESPECT TO AN IMAGINARYCHORD CONNECTING THE FAR ENDS OF THE TERMINAL PORTIONS, A CURVATURERESULTING IN THE END PANEL WHEN FOLDED AT SAID BOTTOM END FOLD LINE WITHRESPECT TO THE BOTTOM PANEL, SAID CURVATURE BEING CONVEX AS VIEWED FROMTHE BOX OUTSIDE WHICH CURVATURE BRINGS THE CENTRAL PORTION OF THE WALLPANEL INTO SUBSTANTIALLY THE SAME PLANE AS THE CORNER LOCK FLAPS WHICHOVERLIE THE END PORTIONS OF THE WALL PANEL ADJACENT SAID CORNER FOLDLINES.